Re: [Xen-devel] [PATCH XEN v6 20/32] tools/libs/foreignmemory: Support err == NULL to map.

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Dec 03, 2015 at 11:22:17AM +0000, Ian Campbell wrote:
> The existing xc_map_foreign_bulk-like interface encourages callers to
> miss error checking for partial failure (by forgetting to scan the err
> array).
> 
> Add support for passing err==NULL which behaves in a
> xc_map_foreign_pages-like manner and returns a global error for any
> failure.
> 
> While documenting this also clarify the overall behaviour and the
> behaviour with err!=NULL.
> 
> With this the compat wrapper of xc_map_foreign_pages() can be
> simplified.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
> v6: New
> ---
>  tools/libs/foreignmemory/core.c                    | 30 
> +++++++++++++++++++++-
>  .../libs/foreignmemory/include/xenforeignmemory.h  | 24 ++++++++++++++---
>  tools/libxc/xc_foreign_memory.c                    | 22 +---------------
>  3 files changed, 51 insertions(+), 25 deletions(-)
> 
> diff --git a/tools/libs/foreignmemory/core.c b/tools/libs/foreignmemory/core.c
> index 21dc7ee..91bea55 100644
> --- a/tools/libs/foreignmemory/core.c
> +++ b/tools/libs/foreignmemory/core.c
> @@ -14,6 +14,8 @@
>   */
>  
>  #include <stdlib.h>
> +#include <assert.h>
> +#include <errno.h>
>  
>  #include "private.h"
>  
> @@ -64,7 +66,33 @@ void *xenforeignmemory_map(xenforeignmemory_handle *fmem,
>                             uint32_t dom, int prot,
>                             const xen_pfn_t *arr, int *err, size_t num)
>  {
> -    return osdep_xenforeignmemory_map(fmem, dom, prot, arr, err, num);
> +    void *ret;
> +    int *err_to_free = NULL;
> +
> +    if ( err == NULL )
> +        err = err_to_free = malloc(num * sizeof(int));
> +

malloc can fail, which means when user passes in err==NULL there is two
possible behaviours of this function?

Wei.

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